Treatment apparatus

ABSTRACT

A probe (1) is designed to propagate and radiate microwave electromagnetic energy in a controlled fashion. The probe (1) includes at least one waveguide (2) of cross-section which would not normally pass microwaves at the operational frequency. The waveguide (2) therefore includes dielectric material (5), such as alumina, in the form of a rod an exposed portion of which forms an antenna. The probe is preferably for use in endometrial ablation and therefore the reduced dimension of the waveguide can be made compatible with the narrow neck of the uterus.

FIELD OF THE INVENTION

This invention relates to apparatus for the treatment of a body by meansof microwave electromagnetic energy. The body is preferably biologicaltissue and, in particular, it relates to apparatus for use in thetreatment of menorrhagia. However, the apparatus may have other uses forthe application of microwave electromagnetic energy to appropriateloads. The invention also includes a method of treatment using theapparatus.

DESCRIPTION OF THE PRIOR ART

Menorrhaaia is a common condition in women over the age of forty andmanifests itself as excessive bleeding from the endometrium whichconstitutes the inner wall of the uterus. The result is exceptionallylong and heavy periods which can be severely debilitating because theblood loss leads to iron deficiency anaemia in addition to the generaldistress and inconvenience which it causes. The most common form oftreatment is to carry out a hysterectomy in which the entire uterus isremoved. However, not only is major surgery expensive but the patientalso has to endure the distress and long period of convalescence. It isfor these reasons that alternative treatments have been sought. Thelining of the uterus which is shed at each menstrual cycle develops fromthe endometrium which is about 5 millimeters thick and covers the wholeof the inner wall of the uterus. Menorrhagia can be cured, or at leastalleviated, if the endometrium is wholly or partially destroyed withoutsurgery. This destruction can either be achieved by physical means or byheating the tissue or a combination of both. In common with most bodytissue, a temperature of around 60° C. maintained in the endometrium forup to 5 minutes will destroy its cells. Because it will no longer bepossible for the endometrium to regenerate the lining the condition willbe cured.

The current known alternative techniques to hysterectomies work withvarying degrees of success but all have disadvantages. The uterus is avery delicate V-shaped pouch-like structure and the opposite walls arenormally separated by a thin film of fluid or may be partly in contact.Therefore it is difficult to gain access to the endometrium for thepurpose of direct physical treatment or for heating it. It isparticularly difficult to treat the tissue immediately surrounding theentrance as heating must be confined to the endometrium itself and notextend to the main body of the uterus and beyond it.

The easiest and least complicated alternative method uses a steel ballabout 5 mm in diameter heated by a monopolar connection to a powersupple. The ball is rolled around in the uterus under the control of thesurgeon to destroy the endometrium. However, the method is timeconsuming and requires highly specialised surgical experience. Even inskilled hands localised burning can occur or other areas are not fullytreated.

It is also known to use certain forms of electromagnetic energy, forexample, cell destruction has been achieved by laser ablation wherelight waves are used. However, laser treatment requires expensive laserequipment and the treatment has to be carried out using highlyspecialised surgical skills.

From European Patent Publication 0407057 it is known to use radiofrequency electromagnetic energy. For example, the method disclosed inthat patent involves placing a radio frequency probe in the uterus andsetting up a radio frequency field between it and a steel belt aroundthe patients waist. The treatment takes up to 45 minutes includinganaesthetic induction and recovery. The procedure itself takes about15-20 minutes and requires the full time attention of a skilledgynaecologist in moving the probe. This is because, as the typical powerused is about 550 watts and radio frequency electromagnetic radiation isdifficult to contain it has to be moved close to the endometrium to beat all effective. It also has the disadvantage that radio frequencyelectromagnetic energy readily passes through most materials (includingtissue) and may very easily leak and insidiously cause injury to boththe patient and surgical staff during the course of treatment.

Another method using radio frequency energy is disclosed in EuropeanPatent Publication No. 0115420 which discloses a device for hyperthermiatherapy using first and second electrodes at al frequency of about 3-30MHZ.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an improved apparatusand method using microwave frequency electromagnetic radiation.

Microwaves at about 2.7 GHz are commonly used for cooking because of thestrong absorption of radiation at that frequency by water. It thereforemight be thought that given the use of light frequency and radiofrequency electromagnetic radiation it would be obvious to trymicrowaves. However, there are no particular restrictions on waveguideor cavity size with microwave ovens therefore a frequency as low as 2.7GHz and a wavelength of 100 cm or more presents no problem.

However, the neck of the uterus can only be dilated to about 10 mmdiameter at maximum and any probe therefore needs to have a diameter ofno more than 8 mm for general use. With conventional design this wouldmean that the microwave frequency would need to be much too high usingconventional waveguide of these dimensions and not enough power would bedelivered to the endometrium i.e. the higher the frequency the less thedepth of absorption by the tissue being treated. It was also thoughtthat standing wave patterns would produce non-uniform heating. However,standing waves only occur where there are reflections present and wehave found that the walls of the uterus rather than causing arereflections absorb the waves by the lossy tissue of the endometriumwhich rapidly reduces the wave to zero before it can reach any potentialreflecting objects.

According to the present invention there is provided a probe forapplying electromagnetic radiation at microwave frequency to a bodycomprising means for receiving microwave signal input of a predeterminedfrequency, a waveguide for receiving and propagating said microwavefrequency input, said waveguide being of a cross-sectional dimensionwhich would not normally pass the microwaves at said frequency,dielectric material within the waveguide, the dielectric constant ofwhich varies the cut-off frequency of the waveguide so that it maypropagate desired modes of the microwaves at said predeterminedfrequency, and an exposed antenna portion at or adjacent an end of theprobe allowing wave transmission away from the probe.

The means for receiving the microwave signal may comprise a secondwaveguide, transition means being provided between the first and secondwaveguides. In this arrangement the first waveguide is suitably acircular waveguide typically of about 10 mm diameter. The secondwaveguide may also be a circular waveguide of about 20 mm diameter. Thetransition means comprises a tapered waveguide interconnecting the firstand second waveguides and loaded with dielectric material.

The dielectric material is preferably in the form of a ceramic rodhaving a tapered end at the transition to optimise transition andextending outwardly beyond the first waveguide to form the exposedantenna portion of the probe. The use of a dielectric filled firstwaveguide in accordance with the invention allows the first waveguide tobe of smaller diameter because, at a given frequency, the wavelength indielectric is shorter. Hence, the diameter of the probe in wavelengthsremains constant throughout transition. For any given wavelength theminimum diameter of the probe is around one half of a wavelength. Anysmaller and the wave will not pass through. The tapered end of theceramic rod overcomes the dielectric mismatch between air In the secondwaveguide and the ceramic material. Without the taper there would be adanger of a reflection at the interface between the first and secondwaveguides.

In an alternative arrangement a single waveguide is provided and themeans for receiving the microwave input directly excites the dielectricfilled waveguide of the desired smaller cross-sectional dimension.

The preferred form of probe includes temperature sensors disposedbetween the first waveguide and a protective sheath. The sensors may beof different lengths in order to detect temperatures at differentlocations along the length of the probe and are united at a temperaturesensor interface.

Although it is preferred that the probe be a single unit it is possiblefor the probe to comprise two or more separable portions. Therefore,according to another aspect of the invention a probe for applyingelectromagnetic radiation at microwave frequency to a body has a firstdielectric stage and a second dielectric stage, the two stages, in use,being operatively connected together the firs. dielectric stagecomprising a first waveguide of a first cross-section; a secondwaveguide of a second cross-section larger than the cross-section so thefirst waveguide for receiving and propagating microwave signal input ofa predetermined frequency, and transition means between the first andsecond waveguides including dielectric material, the dielectric constantof which varies the cut-off frequency of the first waveguide so that itmay propagate said microwave signal at the predetermined frequency; and,the second dielectric stage comprising a probe antenna of dielectricmaterial, a third waveguide about a portion of the dielectric materialand being of substantially the same cross-section as the firstwaveguide, and an exposed antenna portion at or adjacent a free end ofthe probe allowing wave transmission away front the probe.

Preferably, the transition means of the first. dielectric stagecomprises a tapered waveguide interconnecting the first and secondwaveguides, a tapered end on the dielectric material within the taperedwaveguide to optimize transition and a dielectric buffer between thetapered end of dielectric material and the tapered waveguide, thedielectric constant of which is greater than air but less than that ofthe dielectric material.

In this arrangement the probe may be for endometrial ablation and thesecond dielectric stage may include opposed inflatable catheters to aidpositioning in the uterus. Suitably, the second dielectric stage alsoincludes temperature sensing means. Where provided with two stages theprobe includes interface means for the temperature sensing means and forthe inflation of the catheters at the connection between the first andsecond stages of the probe.

If desired, the exposed antenna portion may include guidance means forselective transmission of the microwaves. The guidance means maycomprise a thin metallic layer tapering toward the outer end of theexposed antenna portion to equalise leakage of the microwave energyalong the length of the exposed portion. The metal may be Chromium whichvaries in thickness along the length of the rod instigating adifferential relationship of wave reflection and transmission, thusradiating power evenly across the cylindrical area of the probe.Alternatively the guidance means could be mesh varying in grading alongthe exposed length of the rod or spaced sold rings the spacing betweenwhich is gradually increased.

Where the probe is to be used for medical treatment such as endometrialablation it is important that the probe be sterile for each use.Although it would be possible to provide a disposable probe this isregarded as unnecessarily expensive. Accordingly, preferably the probeincludes a removable and disposable sheath which encapsulates the probeduring use.

Therefore, according to another aspect of the invention there isprovided a protection means for a probe for applying electromagneticradiation at microwave frequency to a body, said protection meanscomprising a sheath having a tubular body which may pass over the probeto encapsulate the operative end of the probe and which issubstantiality transparent to microwaves at the intended frequency ofoperation, and means for securing the sheath in position whereby thesheath may be removed and disbanded after use of the probe. Preferablythe sheath is transparent and the waveguide includes a graticule ormeasurement marking to aid insertion.

The protection means preferably further Includes a disposable handlearranged to receive a probe in use, the handle being locked in positionabout the probe by interengagement with the sheath. The protection meanssuitably includes a unique marking, such as a bar code, to ensure singleuse. the protective sheath may also include a bar code.

Although the probe and apparatus of the present invention may be usedfor any desired application it is preferred that the probe be used forendometrial ablation. Therefore, according to the preferred method ofthe invention there is provided a method of endometrial ablationcomprising the steps of providing a probe as aforesaid having at leastan operative end of outside dimensions no greater khan the dimensions ofa dilated cervix, inserting the operative end of the probe through thecervix into the uterus, applying microwave energy to the probe at afrequency which will be substantially completely absorbed by theendometrium, monitoring the operating temperature to ensure that theendometrium tissue is heated to about 60° C. and maintaining theapplication of the microwave energy for a period of time sufficient todestroy the cells of the endometrium. The microwave energy may beapplied continually or in pulses.

The use of microwave power to heat the endometrium has two mainadvantages. Firstly, electromagnetic radiation at microwave frequenciesis strongly absorbed by tissue and at around 8-12 GHz all microwavepower is absorbed in a layer of tissue about 5 mm thick and it isimpossible for microwave heating to extend beyond this region. This isideal for the treatment of the endometrium which is about 5 mm thick.Secondly, because of this strong absorption, the amount of powerrequired to achieve the desired temperature is relatively small comparedwith RF frequencies and it is likely that the necessary energy could bedelivered over a much shorter period than other current treatments take.If desired the radiation might be pulsed so that the tissue ismomentarily heated above 60° C. and the total treatment time could thenbe shorter still.

The depth of material over which the microwave power is absorbed dependsupon frequency and the material electrical properties. To set this to bearound 5 mm in the endometrial tissue requires a frequency of about 8-12GHz. This frequency then determines the dimensions of the waveguideneeded to carry the wave. If a conventional waveguide were used adiameter of around 20 mm would be required. This is clearly far toolarge to enter the uterus. In accordance with the Invention cut-offwavelength is effectively reduced by the use of high dielectric constantmaterial such as ceramic material or plastics dielectric material orother suitable material which provides a transition to a waveguide ofoutside diameter of about 8 mm.

With the probe of the present invention there is no possibility ofradiation leakage and inadvertent heating occurring outside of theuterus along the Line delivering power to the implanted antenna. Theproblem of delivering power through the narrow neck has therefore beensolved.

Having delivered the power into the uterus, the power is thendistributed uniformly into the roughly flat triangular shaped pouchformed by the uterus by means of the exposed portion of the antennawhich is arranged to prevent radiation escaping close to the input end.The temperature increase necessary to destroy the cells of theendometrium may require only 60 watts of microwave power to provide atreatment time of 2.5 minutes.

It may be found that access to the inner wall of the uterus is difficultand in such a case, there is an attribute of microwaves which can beused to advantage to provide an even distribution of the heating effect.In particular, microwaves will only be strongly absorbed by tissue andnot by any intervening gas. If desired the uterus may be inflated by agas such as carbon dioxide so that the walls will be held away from theantenna and receive an even radiation dose. The gas may be suppliedthrough a central bore formed in the ceramic rod/ If the probe includesinflatable catheters then these may be selectively inflated as requiredto aid insertion and positioning within the uterus. The probe may alsobe provided with fibre-optic vision if desired.

The invention also includes a system for selective microwavetransmission comprising a probe as aforesaid and a source of microwaveenergy. Preferably, the variable parameters of the system are computercontrolled.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example with reference tothe accompanying drawings in which:

FIG. 1 is a diagrammatic side elevation of a preferred probe inaccordance with the invention;

FIG. 2 is a block diagram of the preferred system incorporating theprobe of FIG. 1;

FIG. 3 is a diagrammatic side elevation of a second embodiment of probein accordance with the invention;

FIG. 4 is a block diagram of the system incorporating the probe of FIG.3;

FIG. 5 is a diagrammatic side elevation of a third embodiment of probein accordance with the invention;

FIG. 6 is a diagrammatic side elevation of a fourth embodiment of probein accordance with the invention;

FIG. 7 is a diagrammatic side elevation of a probe in accordance withthe invention including a protective sheath;

FIGS. 8a, 8b and 8c are diagrammatic views of an arrangement forensuring single use of the protective sheath; and

FIGS. 9a and 9b are simplified views showing a probe of the presentinvention in use.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1 a microwave probe (1) has a first circular waveguide (2) of afirst diameter at one end being of custom-determined diameter accordingto probe use and a second circular waveguide (3) of a second, largerdiameter at the other end. The transition between the first waveguide(2) and the larger diameter second waveguide (3) comprises afrusto-conical waveguide (4) and a dielectric rod (5) located mainlywithin the first waveguide (2). The dielectric rod (5) has a tapered end(6) extending into the transition waveguide (4). Disposed about thedielectric tapered end (6) is a dielectric buffer plug (7) havingdielectric properties greater than air but less than that of thedielectric rod (6).

The first waveguide (2) extends towards the free end of the probe (1)but terminates short of the free end to leave an exposed antenna portion(8). The exposed antenna portion (8) and the first waveguide (2) areprovided with a protective removable and disposed sheath (9) ofbio-medically inert and microwave transparent material, for example aprotective PTFE or similar material, which may be profiled as shownaccording to probe use. In order to sense the operating temperature, theprobe (1) includes thermocouple wire temperature sensing means (10).

As can be seen from FIG. 1 the second waveguide (3) also includeswaveguide tuning stubs (11). The stubs (11) are set in the wall of thesecond waveguide (3) to provide means of intrinsically matching theantenna portion (8) in a body. A probe matched to a specific load,preferably endometrium tissue in this application will relieve the needfor extensive pre-operative tuning. In addition, the provision of stubs(11) limit the existence of standing waves in the coaxial feed line (12)which can form there when matching is initiated at the system tuningnetwork end of the coaxial feed line. Standing waves in the coaxial feedline will generate heat and reduce the working life of the cable.

However, subtle load variations from patient to patient can be finetuned using the system tuning network (13) shown in FIG. 2. In FIG. 2,the probe (1) of the invention is supplied with a microwave frequencyinput in the microwave spectrum, preferably in the region of 8-12 GHz,from a microwave frequency generator source and amplifier (14). Theamplified signal is passed to the probe (1) via waveguide line (15) andthe coaxial feed line (12). Although, the provision of stubs (11)permits the tuning of the probe to the specific load, fine tuning isprovided by the tuning network (16) controls the fine turning of thematch of power into the loaded probe. The power level of thesource/amplification unit (14) is monitored by a power sense (17) on thewaveguide line (15). A thermometry unit (18) is provided to taketemperature sensor readings at the probe/tissue interface (1). Thevarious signals are collated and conditioned and fed to a PC/userinterface (19) which may interface with a user's conventional PCgraphics monitor (20). In this way the user may vary the frequency ofthe source (14), set the power level required, and vary the tuningnetwork (16) to achieve optimum match into a load. Also during thetreatment, real-time graphs of temperature data can be viewed on themonitor (20).

In the embodiment of FIGS. 3 and 4 the probe arrangement is similar tothat described with reference to FIGS. 1 and 2 except that the probe isformed in two parts. In FIG. 3 a microwave probe (101) has a dielectricinput stage (102) and a dielectric output stage (103). The input stage(102) includes a circular waveguide (104) of a first diameter at one endand a circular waveguide (105) of a second, smaller diameter at theother end, the diameter being of custom-determined diameter according toprobe use. The transition between the waveguide (104) and the smallerdiameter waveguide (105) comprises a frusto-conical waveguide (106) anda first dielectric rod (107) located mainly within the waveguide (105)but having a tapered end (108) extending into the transition waveguide(106). Disposed about the dielectric tapered end (108) is a dielectricbuffer plug (109) having dielectric properties greater than air but lessthan that of the dielectric rod (107). The circular waveguide (105)terminates in a flange (110) and the rod (107, extends beyond the flange(110) to a joint (111).

The dielectric output stage (103) includes a second dielectric rod(112), an inner end of which abuts the end of the dielectric rod (107 atthe joint (111). The output stage (103) is provided with a furtherwaveguide (113) which extends from the flange (110) towards the free endof the probe (101). However, the waveguide (113) terminates short of thefree end of the probe (101) to leave an exposed antenna portion (114).The exposed antenna portion (114) and the waveguide (113) are providedwith a protective sheath (115) of PTFE or other suitable material aswith the first embodiment. In order to sense the operating temperature,the probe (101) includes thermocouple wire temperature sensing means(130). The temperature sensing means (130) is connected to a temperaturesensor interface (116) at the flange (110).

The probe (101) disclosed by way of example is a probe for endometrialablation and, in order to facilitate insertion of the probe inside theuterus, the probe (101) includes two balloon catheters (117) (only oneshown), one fixed to each side of the waveguide (113). The catheters(117) are provided with air by means of air tubes (118) and an air tubeinterface (119) is provided adjacent the flange (110) on the circularwaveguide (105).

The probe system of FIG. 3 is preferably arranged as disclosed in FIG.4. In that arrangement, it will be seen that the probe (101) is suppliedwith a microwave frequency input in the region of 8-12 GHz from amicrowave frequency generator source (120), the signal of which isamplified by amplifier (121) and passed through a tuning network (122)before entering the input dielectric stage (112) at the circularwaveguide (114). The tuning network (122) controls the match of powerinto a loaded probe (101) and the match is monitored using a power meter(123). Personal computer instrumentation (124) is used to vary thefrequency of the source (120), set the power level required, and varythe tuning network (122) to achieve optimum match into a load. Thiscould also be done manually, if required. A thermometry unit (125) isprovided to take temperature sensor readings from the probe (101)received via the interface (116) and store these on disk in the p.c.(124). During the treatment, real-time graphs of temperature data can beviewed on the monitor (126).

In order to facilitate manipulation of the probe within the uterus, aninflation unit 127 is provided which is operative to supply sufficientair pressure to inflate the catheters (117) on the probe surface.

The probe 140 of the embodiment of FIG. 5 as similar to that of FIG. 3and where appropriate similar references have been used. The maindifference in the embodiment of figure is that the waveguide surroundingthe dielectric rod (107) is formed by thermocouple wire 142 coil edabout the exposed antenna portion 114 for temperature sensing. Theflange 110 is again separable into two parts 144,146 each of whichincludes thermocouple connectors allowing connection of the thermocouplewire 142 to a thermocouple interface 148. In order to serve as awaveguide as well the thermocouple wire 142 is wound so as to providecontrolled radiation along the length of the dielectric rod 107.

The embodiment of FIG. 6 is an alternative arrangement where there is asingle wave guide. In this arrangement a microwave probe 201 has acircular waveguide 202 filled with a dielectric material 23. Thewaveguide 202 terminates short of the end of the probe 201 providing anexposed antenna portion Ant. Towards the end of the probe 201 remotefrom the exposed antenna portion 204 there is a coaxial feed line input205 and a waveguide excitation stud 206. which directly excites thedielectric filled waveguide 202. The probe 201 is matched to the load ofthe body Into which it is to be inserted by means of tuning stubs 207fixed to the wall of the waveguide 202.

As with previous embodiment, the probe 201 is provided with a protectivesheath 208 of PTFF or other suitable material and reference isparticularly directly to the disclosure of one form of the sheath givenin FIG. 7. A temperature sensor 209 is provided between the sheath 208and the waveguide 202 feeding a temperature indicative signal back tothe control (not shown).

In FIG. 7 an embodiment similar to the embodiments of FIG. 3-5 isillustrated where the probe 301 Includes a first waveguide 302 of smalldiameter, a second waveguide 303 of Larger diameter and a frusto-conicaltransition waveguide 304 between the two. The first waveguide includes adielectric rod 305 one end 306 of which is tapered at the transition andthe other end of which provides an exposed antenna portion 307. Therespective waveguides are interconnected by flange fittings 308,309. Thefirst waveguide 302 is protected by a sheath 310 of bio-medically inertmaterial which is substantially transparent to microwave energy of thedesired frequency. The sheath 310 is arrange to interconnect with theflange 309 so as to be removable and replaceable after each use of theprobe. The second waveguide 303 includes an excitation stub 311 whichreceives input from coaxial cable 312. The interconnection between thesheath 310 and the flange 309 is shown diagrammatically but willcomprise a sacrificial joint causing breakage of the sheath 310 onremoval, eg. it may comprise co-operating wedged ribs on the sheath 310and the flange 309 which allow engagement but resist disengagementwithout breakage.

The arrangement of FIGS. 8a, 8b and 8c employs a protective sheath 320and a disposable handle 302 which can be supplied in a sterile pack forsingle use only. In order to ensure disposal of the protective sheath300, and the handle 302 following use, the probe 301, of construction asexemplified in FIG. 1, is housed in the handle 302 for use. The handle302 comprises two halves 303, 304 hinged at hinge points 305, 306. thehandle 302 is moulded of microwave absorbing material and the hingedhalves 303, 304 fold around the probe base and cable 307 leaving thefirst dielectric filled waveguide 308 and antenna portion 309 protrudingfrom the handle as shown.

The two halves 303, 304 of the handle 302 are secured together by meansof the protective sheath and antenna portion 309. The sheath 300 has asacrificial join 310 which fits over the handle halves 303, 304 and canonly be removed by breaking the join 310. The sheath 300 is moulded froma biomedical material that is low-loss to microwaves.

In order to control use of the disposable handle 302 and reference thedisposable items to a systems treatment log, a bar code 311 is usedwhich can be automatically read by a bar code reader (not shown) whenthe assembled probe is placed in a system holster 313. The holster 313is provided on a trolley 314 including the control elements of thesystem described in more detail with reference to FIG. 2. For example, acontrol keypad 315, display arm 316 and display 317 are shown.

In order to ensure that a handle 302 and sheath 300 are used with theprobe 901, the cable 307 suitably Includes a control switch 318 which isoperative by means of a spring switch 319 on the handle 302. The controlswitch 318 is 15 operative through were 320 in the cable 307 which alsoincludes a wire 321 from the thermocouple temperature sensor 322. Thebar code 311 on the handle 302 will be unique and the software of thesystem is designed to reject second use to ensure disposal andreplacement by a new sterile pack comprising handle and sheath for eachtreatment. If desired, the sheath may also include a bar code and thebar code may include batch and date information for data loggingpurposes.

In most applications, and particularly, in the preferred method of theinvention, the probe will be used to apply heat to a load. When the loadis of a biological nature, the addition of temperature sensors in theprobe body as shown in some of the figures is important for safety,monitors allowing for in-situ temperature readings which can be input tofeedback control and data logging systems.

In use, with reference to diagrammatic FIGS. 9a and 9b, the probe 401 ofthe invention is supplied with a microwave frequency or put in theregion of 8-12 GHz from microwave frequency generator. The dielectricmaterial 402 within the first waveguide optimists a smooth transitionwithout causing undue reflection. The probe 401 is suitably providedwith a handle allowing manipulation by the operator and providingsterile single use as described by way of example with reference toFIGS. 8a, 8b, 8c.

The patient is prepared by drugs being administered to contract theendometrial layer 403 of the uterus 404 as necessary. The cervix 405 isdilated and the surgeon, will then insert a tool (not shown) todetermine the depth of the uterus 404 to determine the area fortreatment. The probe 401 is then inserted into the uterus 404 and theprobe tip 406 positioned using markers 407 on the length of the probe asshown diagrammatically.

When the applicator tip is placed in biological tissue the generatedfield shape 408 in the tissue 409 can be a uniform sphere-like shape ofabout 4-5 mm from the dielectric surface of the probe tip 406 as showndiagrammatically in FIG. 9a.

Electromagnetic heating of the tissue 409 only occurs within thissphere.

In the particular treatment disclosed the probe 401 is inserted to thefundus of the uterus 404 and the probe 401 slowly withdrawn to exposethe full endometrial lining to the electromagnetic field. The microwaveelectromagnetic energy radiated from the exposed probe tip 406 heats thelocalised area of endometrium 43 and during treatment the temperature iscontinually monitored by means of the temperature sensors. Thus, forexample, the power may be switched on for a period of 9 seconds and thenswitched off for a period of 1 second whilst the temperature ismeasured. Whilst the control in this respect may be manual it ispreferred to provide an automatic control system for maintaining thecontrolling temperature by means of the fibre-optic thermometry systemsand data acquisition and control means.

The microwave energy is strong absorbed by the tissue of the endometriumand, by controlling the frequency and the power, the depth of absorptioncan be restricted solely to the endometrium itself which is about 5 mmin depth. This has the advantage that physical injury or radiationeffects on surrounding tissue are avoided. The markers 407 on the probe401 assist the surgeon in knowing where the probe tip 406 is in theuterine cavity during treatment.

The treatment time is likely to be less than 20 minutes minimisinggynaecclogist time and allowing the patient a minimum time in hospitaltypically 1 day or less. The treated endometrium is left as scar tissue.

Although, the invention has been described using substantiallycontinuous heating using lower power eg 60 watts to achieve atemperature in excess of 60° C., the microwave electromagnetic energymay be pulsed at a much higher power by means of a pulse magnetron. Thisprovides pules of kilowatt power in microseconds each pulse being spacedby the order of a millisecond. For example, it may be possible toprovide pulses with a peak output of 80 kilowatts for a duration of 1microsecond spaced by 1 millisecond. Pulsing may have the advantage ofcountering the body's natural reaction to continuous heating of tissueof increasing the blood flow to the area being treated to providecooling. Thus continuous heating may not be as efficient in destroyingthe cells as pulsed heating where the effect of the increased blood flowis minimised or not even promoted in the first instance.

From the drawings it will be seen that the probe of the presentinvention is designed to propagate and radiate microwave electromagneticenergy in a controlled fashion. The design makes use of a dielectricmaterial within a circular waveguide with dimensions dictated by themicrowave frequency used and the electrical properties of the dielectricmaterial. The preferred dielectric material is alumina which provides anantenna diameter which is compatible with the narrow neck the uterus.However, choosing a material with a higher dielectric constant, thisdiameter could be made even smaller. The dielectric material may beceramic, plastics or other suitable material.

Although, the choice of dielectric material will fix the probe diameter,the tip of the exposed antenna portion will be shaped to achieve thedesired radiation pattern. The profile of the protective sheath can alsobe shaped to provide more accurate coverage of radiation in aspecifically shaped load. In certain applications part of all of theprobe may be designed to swivel or rotate to achieve better radiationcoverage across a load. Thus, careful design of the shape and size ofthe probe will automatically match it to an application specific load,thus reducing the effects of standing waves which can cause loss ofpower and hot spots. This optimum matching can be offset by the varianceof load shape and size. Tuning can be done by introducing tuning screwsinto the antenna/waveguide body or by adding specifically designed metaltuning washers into the dielectric/antenna assembly.

The protective sheath is, preferably of a sterile, single use, anddisposable design will be used to provide a medically inert external forall parts of the probe that come in contact with a body. The materialwill be medically inert, low-loss at microwave frenzies, capable ofwithstanding extended exposure to harsh chemicals and high temperatures,and it will lend itself to production molding techniques. The protectivesheath suitably includes a bar code to ensure single use to preventcross-contamination and to provide traceability.

As an alternative to bar codes, the unique identification means maycomprise any other suitable means, eg. a passive electronic transporterwhich, if desired, may be embedded in the material of the protectivesheath and/or the handle.

We claim:
 1. A probe for applying electromagnetic radiation at microwavefrequency to a body region accessible through an opening of the body,comprising:an input for receiving microwave signal input of apredetermined frequency; a first waveguide for receiving and propagatingsaid microwave frequency input, said waveguide having an externaldiameter that fits within the opening and being of a cross-sectionaldimension which would not normally pass the microwaves at saidfrequency; dielectric material within the first waveguide, thedielectric constant of which varies the cut-off frequency of thewaveguide so that the waveguide can propagate desired modes of themicrowaves; and a portion of dielectric material protruding from thewaveguide at the active end of the probe and forming an antenna which isshaped to control wave transmission away from the probe; whereby thefirst waveguide is insertable through the opening to place the antennain operative relation with a body region.
 2. A probe according to claim1, wherein the tip of the exposed antenna portion is shaped to achieve adesired radiation pattern.
 3. A probe according to claim 1, wherein thefirst waveguide is a waveguide of circular cross-section.
 4. A probeaccording to claim 1 wherein the input for receiving the microwavesignal comprises a second waveguide, air filled with a largercross-sectional dimension than the first waveguide and a taperedwaveguide section interconnecting the first waveguide with the secondwaveguide so as to provide transmission of the microwaves with minimalreflection at the interface between the first and second waveguides. 5.A probe according to claim 4, wherein the dielectric material taperswithin the tapered waveguide section to optimize transmission of themicrowaves with the minimal reflection.
 6. A probe according to claim 4,wherein the second waveguide includes tuning stubs providing meansadapted for matching the antenna to the load of the body into which theprobe is to be inserted.
 7. A probe according to claim 3, wherein thereis a single waveguide and the input for receiving the microwave inputdirectly excites the dielectric filled waveguide of the desired smallercross-sectional dimension.
 8. A probe according to claim 7, wherein theinput for receiving the microwave input comprises a co-axial feed lineinput and a waveguide excitation stub which directly excites thedielectric filled waveguide.
 9. A probe according to claim 7, whereinthe probe is adapted to be matched to the load of the body into which itis to be inserted by means of tuning stubs secured to a wall of thewaveguide.
 10. A probe according to claim 1, including temperaturesensing means.
 11. A probe according to claim 10, wherein thetemperature sensing means is disposed between the first waveguide and aprotective sheath.
 12. A probe according to claim 1, includes aprotective sheath which encapsulates the probe during use.
 13. A probeaccording to claim 12, wherein the protective sheath provides amedically inert external coating for all parts of the probe that comeinto contact with a body.
 14. A probe according to claim 12, wherein theprotective sheath is a sterile, single-use and disposable sheath andwhich comprises a tubular body which is substantially transparent tomicrowaves at an intended frequency of the operation, which, in use, maybe passed over the probe to encapsulate the operative end of the probe;and means whereby the sheath may be secured in position during use ofthe probe and may be removed and discarded after use of the probe.
 15. Aprobe for applying electromagnetic radiation at microwave frequency to abody region accessible through an opening of the body, comprising:meansfor receiving microwave signal input of a predetermined frequency; afirst waveguide for receiving and propagating said microwave frequencyinput, said waveguide having an external diameter that fits within theopening and being of a cross-sectional dimension which would notnormally pass the microwaves at said frequency; dielectric materialwithin the first waveguide, the dielectric constant of which varies thecut-off frequency of the waveguide so that the waveguide can propagatedesired modes of the microwaves; a portion of dielectric material at oradjacent to the active end of the probe forming an antenna whichcontrols wave transmission away from the probe, whereby the firstwaveguide is insertable through the opening to place the antenna inoperative relation with a body region; the means for receiving themicrowave signal comprising a second waveguide, air filled with a largercross-sectional dimension than the first waveguide and a taperedwaveguide section interconnecting the first waveguide with the secondwaveguide so as to provide transmission of the microwaves with minimalreflection at the interface between the first and second waveguides; thedielectric material tapering within the tapered waveguide section tooptimize transmissions of the microwaves with the minimal reflection;and a dielectric buffer inside the tapered waveguide section, thedielectric constant of which is greater than air and less than that ofthe dielectric taper.
 16. A probe for applying electromagnetic radiationat microwave frequency to a body region accessible through an opening ofthe body, comprising:means for receiving microwave signal input of apredetermined frequency; a first waveguide for receiving and propagatingsaid microwave frequency input, said waveguide having an externaldiameter that fits within the opening and being of a cross-sectionaldimension which would not normally pass the microwaves at saidfrequency; dielectric material within the first waveguide, thedielectric constant of which varies the cut-off frequency of thewaveguide so that the waveguide can propagate desired modes of themicrowaves; a portion of dielectric material at or adjacent to theactive end of the probe forming an antenna which controls wavetransmission away from the probe, whereby the first waveguide isinsertable through the opening to place the antenna in operativerelation with a body region; and temperature sensing means disposedbetween the first waveguide and a protective sheath, and comprisingsensors disposed at different locations along the length of the probe todetect the temperatures at said different locations.